Conventionally, an accumulator including a metal bellows has been used in order to perform release of a large amount of energy for a short time, diminishment of pressure fluctuations, and the like. In such an accumulator, in order to suppress the metal bellows from colliding with a pressure vessel when the metal bellows is oscillated due to external oscillation, a slide ring also having a bearing function is provided at the tip of the metal bellows. However, only the slide ring may be insufficient under various conditions such as the length of the metal bellows. Under such circumstances, an intermediate ring (damping member) exhibiting the same function as that of the slide ring may also be provided at the intermediate position in the axial direction of the metal bellows. Such a technology will be described by reference to FIG. 11. FIG. 11 is a schematic cross sectional view of an accumulator in accordance with a conventional example.
An accumulator 500 in accordance with a conventional example has a pressure vessel (shell) 510, and a port forming member 520 provided so as to close the opening of the pressure vessel 510, and having a port. Then, the pressure vessel 510 is provided therein with a metal bellows 530 which is a constituent member of a partition unit for partitioning the space in the vessel into a gas chamber (G) including a gas sealed therein, and a fluid chamber (L) including a working fluid flowing therein. At the tip of the metal bellows 530, a slide ring 540 also having a bearing function is provided. The slide ring 540 is configured such that the outer circumferential surface thereof is slidable with respect to the inner circumferential surface of the pressure vessel 510. This allows the metal bellows 530 to be expanded and contracted smoothly, and suppresses the oscillation of the metal bellows 530. However, depending upon various conditions, the vicinity of the intermediate part of the metal bellows 530 may collide with the inner circumferential surface of the pressure vessel 510. Under such circumstances, in the conventional example, an intermediate ring (damping member) 590 is provided at the intermediate position in the axial direction of the metal bellows 530.
The intermediate ring 590 includes a thin sheet annular trunk part 591, and a guide part 592 having a wider width in the expansion and contraction direction (equal to the axial direction) of the metal bellows 530 than the width of the trunk part 591. A plurality of the guide parts 592 are provided spaced apart from one another in the circumferential direction on the radially outward side of the trunk part 591. The radially outward surface of the guide part 592 is formed slidably with respect to the inner circumferential surface of the pressure vessel 510. As a result, the function of guiding the movement of the trunk part 591 is exerted. The intermediate ring 590 formed as described up to this point exerts the same function as that of the slide ring 540. For this reason, even in the vicinity of the intermediate part of the metal bellows 530, the expansion and contraction of the metal bellows 530 become smooth, so that the oscillation of the metal bellows 530 is suppressed.
However, with the intermediate ring 590 in accordance with the conventional example, a gap is formed between the radially inward tip of the trunk part 591 and the valley part of the metal bellows 530. Further, the tips of the crest parts of the metal bellows 530 are configured so as to abut on the radially inward surface of the guide part 592. For this reason, when the intermediate ring 590 receives an impact from the inner circumferential surface of the pressure vessel 510 due to the oscillation of the metal bellows 530, the impact is transmitted via the guide part 592 of the intermediate ring 590 to the crest parts of the metal bellows 530 without much diminishment of the impact. Therefore, the crest parts of the metal bellows 530 may be deformed or broken.
Further, with the metal bellows 530 being contracted, the gap between the belly parts of the metal bellows 530 becomes narrower. For this reason, in order to prevent the expansion and contraction of the metal bellows 530 from being affected, it is necessary to reduce the thickness of the trunk part 591 of the intermediate ring 590 (equivalent to the width in the expansion and contraction direction (equal to the axial direction) of the metal bellows 530). As a result, with the metal bellows 530 being expanded, a large gap is caused between the belly parts of the metal bellows 530 and the trunk part 591 of the intermediate ring 590. For this reason, the mounting state of the intermediate ring 590 is unstable. Further, there is no stability during sliding.